The present invention relates to the general field of diesel internal combustion engines, and more particularly relates to an intake air throttling device for a diesel internal combustion engine which can provide good anti vibration and anti noise protection, both during idling operation and during stopping of the diesel internal combustion engine.
Typically the load on a diesel internal combustion engine, i.e. the power output produced thereby, is regulated by controlling the amount of fuel injected into the combustion chamber or chambers thereof, rather than, as is the case with a gasoline internal combustion engine incorporating a carburetor, by regulating the amount of intake air flow. Thus, when the diesel internal combustion engine is required to produce a considerably high power output, i.e. is required to operate in a medium or a high load operational condition, then a considerable amount of fuel is injected into each combustion chamber thereof at each of its compression strokes; and, on the other hand, when said diesel internal combustion engine is required to produce a low power output just sufficient to keep the engine itself operating, i.e. is required to operate in an idling operational condition, then a much smaller amount of fuel is injected into each combustion chamber thereof at each of its compression strokes.
In a simplest form of conventional prior art, the intake air passage of the diesel engine is left wide open at all times, and therefore enough intake air is available for even high load operation of the engine wherein the pulses of injected diesel fuel which are injected into the combustion chambers are of maximum amount; and, correspondingly, the amount of intake air sucked in to the combustion chambers during idling engine operation wherein the pulses of injected diesel fuel which are injected into the combustion chambers are of quite small amount is very excessive - but this need not present any insuperable problem, although in this case the engine operates in a very over lean operational mode.
However, a problem which often occurs with diesel engines, especially small diesel engines such as are being used more and more these days in automotive applications for passenger cars, is that noise and vibration during engine idling operation are excessive, and can produce user complaints, as well as deteriorating the service lift of such a diesel engine. Accordingly, some means of restricting the idling vibration and noise levels has become a desirable design goal.
In the prior art, a known method of thus improving engine idling operation of a diesel internal combustion engine has been to somewhat throttle the air intake passage of the engine during idling operation thereof, as by using a throttling valve or the like. This has been very useful for reducing noise and vibration during engine idling, and various systems have been proposed for control of such a throttling valve.
Another problem which has been remarked upon with regard to diesel internal combustion engines is that during stopping of the engine, i.e. when during operation of the engine the key switch or the like controlling said engine is switched to the OFF state from the ON state (or the like) and according to this supply of injected pulses of diesel fuel into the combustion chamber or chambers of the diesel engine is terminated, then considerable vibration and noise are liable to be caused. Again, this can produce user complaints, as well as deteriorating the service life of such a diesel engine. Accordingly, again, some means of restricting such stopping vibration and noise levels has become a desirable design goal.
In the prior art, a known method of thus improving engine stopping operation of a diesel internal combustion engine has been to totally close the air intake passage of the diesel internal combustion engine during stopping operation thereof. This is often done in large diesel engines by using a manually controlled throttling valve or the like, and has been very useful for reducing noise and vibration during engine stopping.
Meanwhile, of course if the air intake passage of the diesel internal combustion engine is to be restricted at any time it is important that at no time should the air intake passage be restricted to such an extent as to prevent the entry into the combustion chamber or chambers of the diesel internal combustion engine of sufficient air to completely combust all of the diesel fuel which is being injected into said combustion chamber or chambers. If undesirably the air supply to the combustion chamber or chambers should thus be over restricted, generation of an undesirably large quantity of diesel smoke will most likely occur, as well as the emission in the exhaust gases of the diesel internal combustion engine of an undesirably large quantity of noxious components.